Electric drive to be employed in a drilling rig



Nov- 1970 o. LMARYANOVSKY EI'AL- 3,53

ELECTRIC DRIVE TO BE EMPLOYED IN A DRILLING RIG Filed Sept. 26, 19e

United States Patent 3,538,363 ELECTRIC DRIVE TO BE EMPLOYED IN A DRILLING RIG David Isaakovich Maryanovsky, 11 Parkovaya 44, korpus 1, kv. 8, Moscow, U.S.S.R.; Solomon Yakovlevrch Kagan, Moskovsky prospekt 96, kv. 71, Kharkov, U.S.S.R.; Dzandar Avsimaikhovich Takoev, Volzhsky prospekt 39, kv. 45; Vasily Vissarionovich Pekhvlashvili, Ulitsa Krasnoarmeiskaya 19; and Valentin Lavrovich Trifonov, Ulitsa Aerodromnaya 28, kv. 24, all of Kuibyshev, U.S.S.R.

Filed Sept. 26, 1968, Ser. No. 762,939 Int. Cl. H02k 49/04 US. Cl. 310-98 1 Claim ABSTRACT OF THE DISCLOSURE An electric drive for a drilling rig winch has a flywheel connected rigidly to an inductor of an electromagnetic clutch, there being an armature accommodated Within the inductor to impart rotation to a hoisting shaft of the winch. At least two are stators surround the flywheel and are operatively associated therewith to start the same as a common rotor. Thus the flywheel serves both as a rotor and as an inertia member.

The present invention relates generally to drilling rigs and more particularly to flywheel-type electric drives employed in drilling rig winches.

Known in the art are drilling rigs featuring combination drives, i.e. diesel and diesel-electric drives, wherein diesels impart rotation to the flushing pumps and electric generators.

As the flushing pumps are inoperative when lowering or hoisting the tools involved, and the hoisting shaft of the winch is not involved in operation when tripping, the diesels in the process of tripping impart rotation directly to the flushing pumps, whereas when lowering and hoisting the tools, said diesels impart rotation to the generator adapted to feed electric motors of the winch mechanisms.

Besides, for a drive of the pumps requiring no frequent startings, operating continuously for a relatively prolonged period at a constant load and consuming a larger portion of power assigned for well drilling, such a diagram of the drilling rig, especially when the most progressive method of drilling such as turbo-drilling is involved, makes it possible to utilize the diesel power directly without transformation and, consequently, without any losses, whatever.

Furthermore for a drive of the winch mechanisms, and mainly of motors adapted for hoisting operations which require frequent startings, short-time applications of great torques and which are adapted to operate under sharply varying loads but which consume only a small portion of power assigned for well drilling, the power of the diesel is converted into electric energy capable of supplying the motors of the winch mechanisms with the resultant power losses which are insignificant as to their absolute values.

Such a drilling rig suffers from the following disad- I 3,538,363 Patented Nov. 3, 1970 introduce alterations into the design of the regulating member of the diesel involved. Moreover, it will require the employment of special means capable of preventing the diesel generators from dropping out of step when sharp decreases or increases in the load are encountered, which fact will substantially complicate servicing of .the drilling rig in question.

Insofar as the second case is concerned, the application of two or more electric motors for a drive of the winch hoisting shaft will complicate the design of the winch thereby bringing down the effect of the employment of the combination-drive system.

There are likewise known drilling rigs with their winch electric drive featuring a flywheel that are adapted to be utilized in the electrified regions.

Such a drilling rig features a phase-wound rotor induction motor which is adapted to accelerate the fly wheel and whose stator is constantly connected to the buses of the substation meant for supplying the drilling rig in question. The winch hoisting shaft is imparted rotation from a flywheel through a clutch which is essentially a birotative synchronous machine and is so accommodated within the flywheel rim that one member, such as inductor (or armature), constitutes an integral part with the rim, whereas the other member of said clutch, e.g., armature (or inductor), is rigidly connected to the winch hoisting shaft through a reduction unit. Resistors partially short-circuited by the contacts of the contactors are constantly connected to the clutch armature. The clutch inductor is supplied with direct current which, when being varied, makes it possible to vary the torque transmitted from the flywheel to the winch hoisting shaft.

The birotative synchronous machine is so made that the maximum torque developed by it for a short period (of the order of a few seconds) may be several times as high as the stalling torque of the induction motor.

The drilling rig described above employing such a drive suffers from the following disadvantages.

The winch drive of such a drilling rig may be used in electrified regions only, since in the case of a diesel electric drive either synchronization of the units of the diesel generators is required or accelerating of the flywheel from a plurality of electric motors the number of which equals that of the diesel generators involved.

The complicated design and certain difficulties in servicing the flywheel unit are due to the fact that said flywheel unit features a built-up shaft, as well as due to the provision of an inner hearing which is difficult to be lubricated.

Besides, the presence of a starting motor considerably increases overall dimensions of the unit, in particular its frame and foundation.

It is a primary object of the present invention to eliminate the above-mentioned disadvantages inherent in the drilling rigs employing both the combination drive and the flywheel-type electric drive.

The invention is aimed at the development in such a flywheel-type electric drive of a drilling rig winch that would feature a simplified design and the utmost posible small dimensions and weight enabling the drilling rig to be made so that it would possess the advantages of the drilling rigs which make use of both the combination drives and the flywheel-type electric drives and would not be subject to the disadvantages thereof.

According to the invention, said object is accomplished by the fact that in the electric drive of a drilling rig winch incorporating an induction motor provided with a flywheel and an electromagnetic clutch which is essentially a birotative synchronous machine provided with both an inductor accommodated within the flywheel rim and constituting an integral part therewith, and an armature rigidly connected to the winch hoisting shaft, said'drive motor is provided with at least two are stators, wherein the flywheel serves as a common rotor thereof.

The drive made according to the present invention makes it possible to provide a drilling rig featuring the following advantages:

A drilling winch may be implemented as a single-speed winch according to a simple functional diagram which fact makes the gearbox unnecessary. Besides, the number of chain transmissions and pneumatic type clutches is reduced to a minimum, said pneumatic type clutches of the winch being engaged only when immobile. Moreover, the entire design of the drilling rig becomes more simplified since it is devoid of a mechanical drive from the diesels to the winch and the group drive of the mechanisms is replaced by an individual electric drive.

The drilling rig provided with an electric drive and with arc stators, is made identical for both cases, i.e. when power is supplied from the supply mains, if used in electrified regions and when power is supplied from the diesel generator. Changing over from the power supply from diesel electric drive to the power supply from the mains for a serviceable drilling rig may be effected during a few hours.

Besides, the average speed of hoisting of the tools may be made equal to the maximum permissible speed of lowering of the tools involved, i.e. the above-mentioned average speed may be increased 3 to 4 times as compared with the speeds of hoisting of the maximum Weight tools for the conventional winches.

When the flywheel rotates, the birotative synchronous machine is used as a braking means adapted to control the speed of the winch drum when lowering each string due to which fact the speed of lowering of the string is substantially reduced.

Moreover, a smooth fitting of the tools onto the rotor table is effected without a mechanical brake which is used only as an emergency one, as well as for fixing the tools in position when immobile thereby providing the possibility to dispense with an electric or hydraulic brake.

To accelerate the flywheel from the minimum up to the rated speed the required power of the arc stators will be 3 to 4 times as low as the installed power of the motors employed in conventional winches that would be necessary to obtain the same average hoisting speed for the tools of maximum weight.

The changeover from the hoisting of the tools involved to the lowering thereof is effected by changing the exciting current of the exciter only. The control of the winch is by merely shifting a handle which is adapted to set any speed at either of the duties, and in particular a zero speed, i.e. the tools are suspended without applying a mechanical brake. Moreover, a small power required to effect the control of the winch makes it possible to provide full automation of the drilling winch, according to an extremely simple design.

The torque applied to the winch drum is varied smoothly due to which fact the Wear of the wire rope is diminished.

Besides, the replacement of the stock of tools and the brake shoes is not required.

When each of the arc stators is supplied from its particular diesel generator, the speeds of the diesels involved will be the same at any duties and will vary smoothly and slowly depending upon the speed of the flywheel, with the resultant increase in the lifetime of the diesels in question. The torques of the diesels are summed up, whereas the load is automatically distributed therebetween into equal portions without applying any special means.

In case the arc stators are supplied from the mains the maximum torque developed by the clutch is not dependent upon the voltage variation of the supply mains. Current rushes with startings at small static torques are not observed. The total number of current rushes is several times as low as in an electric drive employed in conventional winches. Moreover, if the mains supply is discontinued in case of emergency, the tools can be hoisted during a few seconds up to the height equal to that of the string by the energy stored in the flywheel.

Alongside with the abovesaid, the diesels are accommodated in locations specially adapted for the purpose, which improves working conditions at the drilling rig.

The invention will be described hereinbelow by way of an exemplary embodiment of a drilling rig with reference to the accompanying drawing, wherein represented, according to the present invention, is an elementary diagram of an electric drive with a flywheel and are stators which are supplied from diesel generators.

The essence of the electric drive for a drilling rig, shown in the diagram, relies on the assumption that both the hoisting and lowering of the tools up to the height equal to that of one string, i.e. the time intervals when the drive is to develop respectively a traction or braking torque, alternate with time intervals when the Winch drive is disengaged or is idle. Thus, the drive of a drilling winch is featured by an intermittent duty, the duty cycle factor being of the order of 25 to 30%.

The alternation of the on-load and no-load cycles provides the possibility to introduce between the motor fed either from the supply mains or from a diesel generator, and the hoisting shaft of the winch, an energy storage (a flywheel) and an electromagnetic clutch made as a synchronous machine provided with a rotating armature and an inductor.

It is due to the fact that the time required for consump tion of energy to effect a hoisting cycle is several times as low as that required for accumulating said energy, the power necessary to start the flywheel is likewise several times as low as that required to hoist the tools of the same weight at the same speed.

As it is clearly seen from the drawing, the drum 1 of the drilling winch, through a pneumatic clutch 2 and a reduction unit, 3 is connected to an electromagnetic clutch.

The electromagnetic clutch is made as a birotative synchronous machine provided with a rotating armature 4 and an inductor 5 which is constructionally combined with a flywheel 6.

The flywheel 6 is started by means of arc stators 7. The are stator 7 is essentially a three-phase winding with a magnetic core embracing a portion of the outer surface of the rim of the flywheel 6.

Each of the arc stators 7 is connected to a source of a three-phase voltage and is capable of developing a torque applied to the flywheel '6. The flywheel 6, apart from its main purpose to store the kinetic energy, is used as a rotor of a starting motor.

If the velocity of the field of the arc stator is larger than the speed of the flywheel, the torque thus arising will start accelerating the flywheel whose speed will tend to increase, thus approaching the velocity of the abovementioned field.

Otherwise, the field involved will brake the flywheel and the energy thereof, though the winding of the arc stator will return to the supply source.

Besides, due to a considerable weight, large cooling surface and great speed of the flywheel rim, it is possible to remove a considerable amount of heat from said rim. Therefore, the flywheel can replace not only the rotor of a starting motor but also the resistors connected to the winding thereof.

In the electrified regions the arc stators are constantly connected to the supply mains and are disconnected therefrom by oil circuit breakers from time to time.

In the case of a diesel drive each arc stator is connected to its particular generator.

As the flushing pumps are inoperative when lowering or hoisting the tools, and the hoisting shaft of the winch is not involved in operation when tripping, the diesel drive of the flushing pumps can be likewise employed to impart rotation to the generators.

In this case a synchronous generator 13 is rigidly connected to the shaft of each diesel 8 adapted to impart rotation to a flushing pump 9 through a pneumatic clutch 10, a reduction unit 11 and a belt drive 12.

As it is seen from the diagram of the herein-disclosed electric drive of a drilling rig, each synchronous generator supplies its particular are stator. Due to the fact that the drilling rig employs not less than two water pumps at a time, at least two are stators must be provided to start the flywheel, each of said stators being capable of starting its particular flywheel independently.

The power supply of the arc stators, according to the represented diagram, makes it possible to synchronize the generators and to sum up the torques of the diesel engines when starting the flywheel or when the speed thereof is decreased. Maintaining their rated torque, the diesel engines smoothly vary their speed within the range depending upon the speed variation of the flywheel when hoisting the tools of the maximum weight, the generators adapted to supply the arc stators being automatically kept to rotate synchronously. Such an operating duty of the diesel engines in question adds much to the service life of said engines.

The inductor is supplied with a controlled direct current from an exciter 14 rotated from the flywheel shaft through a belt drive 15. A means adapted to control the exciting current of the exciter 14 is not shown in the diagram.

When hoisting or lowering the tools the field of the inductor 5 generates in the armature winding a voltage to be applied to load resistors 16.

As the speed of the armature 4 when hoisting the tools, gradually increases to reach the speed of the flywheel, sections 16 of the resistors gradually get short-circuited by contact groups 17 and 18 of the corresponding contactors not shown in the diagram.

The coils of said contactors are supplied with voltage difference across tacho-generators 19, one of which is adapted to measure the speed of the armature 4, whereas the other is adapted to measure the speed of the inductor 5 and the flywheel 6.

When sinking a well, the flywheel 6 and the exciter 14 rotatable therefrom, both rotate at a rated speed, since the electromagnetic clutch is ready to hoist the tools at any moment, the armature 4 being disconnected from the drum of the winch 1 to be immobile, since the busbarpneumatic clutch is disengaged and the winding of the inductor 5 is de-energized.

The exciter 14 while rotating and not loaded in the course of sinking, can be used at that moment to automatically feed the tools, according to the Ward-Leonard system.

Besides, to feed the tools use is made of a DC. machine 20 which is connected to the shaft of the winch 1 through a speed reduction unit 21, a belt drive 22 and a pneumatic clutch 23.

When sinking a well, the armature of the exciter 14 is disconnected from the inductor 5 and is connected to the armature of the DC. machine 20. Automatic feeding of the drilling tools in this case can be provided by controlling the current in the field winding of the exciter 14.

Variation in the value of DC. current supplying the inductor 5 is the only parameter involved in controlling the electromagnetic clutch. Therefore no forces arise between the inductor and the armature 4 until D.C. current is applied to the winding of the inductor 5, the armature 4 being either immobile, if the tools are being lowered, or rotated in the direction opposite the rotation of the inductor 5 and the flywheel 6.

Once the inductor 5 has been switched on, an A.C. three-phase current appears in the armature 4, said current being capable of creating the torque and causing the armature to rotate in the direction of the flywheel rotation.

While giving off the energy stored in the flywheel, the latter is losing its speed. When hoisting the tools of the maximum weight up to the height equal to that of the string, the flywheel speed must not decrease more than two times as compared to the rated one.

Once the string has been completely hoisted, it is screwed off, transferred onto the string holder and the hook is lowered to initiate a new hoisting operation, during which procedures the flywheel is being accelerated thus again accumulating the energy.

When the tools are being lowered, rotation of the electromagnetic clutch armature is reversed with respect to that when hoisting the tools.

Therefore the voltage of the tacho-generator 19 which is connected to the shaft of the armature 4 reverses its sign, the contactors are interlocked and the resistors 16 are wholly connected into the circuit of the armature.

The lowering of the tools through the use of the electromagnetic clutch is accomplished as follows.

With the winding of the inductor 5 energized, the drum of the winch is released and the tools start to freely lower at an increasing speed, thus causing the armature 4 of the electromagnetic clutch to rotate in the direction opposite to that of the inductor 5 with the flywheel 6.

When the speed of lowering the tools, while increasing, reaches the maximum permissible one prescribed by the safety rules, the winding of the inductor 5 gets energized. The braking torque corresponding to the armature speed at the instant the inductor is switched on, must exceed the moment arising due to the lowering of the tools in question.

Besides, the speed of lowering starts to decrease, whereas the braking torque tends to increase. If after the moment of deceleration the inductor is kept switched on, it will first lead to stoppage of the instrument involved and then to the hoisting thereof. The manual lowering of the instrument can be effected either by periodically cutting in or off the inductor winding, or by controlling the current of the inductor 5.

The employment of the electromagnetic clutch for the purpose of decoupling the drilling winch provides the possibility to freely accelerate the tools being lowered up to the maximum permissible speed and to control the speed when lowering each string.

The changeover from the hoisting of the instrument to the lowering thereof can be accomplished by varying the exciting current only. The tools may be kept suspended without applying a mechanical brake.

What is claimed is:

1. An electric drive to be employed in a drilling rig winch provided with an induction motor, said drive comprising: a flywheel; an electromagnetic clutch essentially constituted as a birotative device including an inductor rigidly connected to said flywheel; an armature accommodated within said inductor and adapted to impart rotation to a hoisting shaft of the winch; and at least two are stators operatively associated with said flywheel to start the same as a common rotor.

References Cited UNITED STATES PATENTS 2,246,372 6/1941 Lockwood et al. 31098 X 2,675,494 4/1954 Ellis 310166 FOREIGN PATENTS 754,140 8/1956 Great Britain.

DAVID X. SLINEY, Primary Examiner U.S. c1. X.R. 

